Mono and bis (meth)-acrylates, and uses thereof

ABSTRACT

(Meth)-acrylate compounds having one or two terminal (meth)-acrylic acid groups on an oligomer chain which have low volatility and are liquid to solid at room temperature, wherein the oligomer chain is mainly in the form of a polyester oligomer formed from one or more hydroxycarboxylic acids. The preferred (meth)-acrylate compounds are based on polyester-oligomers with a mean molecular weight in the range of about 200 to 600. The invention also relates to the use of these new reactive (meth)-acrylate compounds in construction adhesives.

This is a continuation-in-part of pending application Ser. No. 726,278filed April 24, 1985 now abandoned, which is a continuation ofapplication Ser. No. 460,900 filed on Jan. 25, 1983, now abandoned.

BACKGROUND OF THE INVENTION

Within the group of reactive adhesives the methacrylate systems arebecoming increasingly important. They have been commercially availablefor years as a two component formulation. Component A (adhesivecomponent) usually exists as a solution of elastomers in a monomer or amonomer mixture based on acrylic acid and/or especially methacrylicacid. Component B (activator or hardener component) contains aninitiator to initiate free radical polymerization.

Both components prior to their use are thoroughly mixed together,thereby starting the polymerization of the monomers.

A further development of the so-called two component systems are the"No-Mix" or "Second Generation Acrylate adhesives". The use of theseadhesives is similar to that of the contact adhesives, i.e. theinitiator component is first applied as a thin layer on one or both ofthe surfaces to be glued together. After a waiting period, which can beup to several hours, the adhesive component is then applied. The bondingis carried out by fixing the components in the desired position.

In the adhesive component polymerizable monomers can be used alone or incombination, especially methacrylic acid or a methacrylic acidderivative such as methyl methacrylate, or suitable acrylic acidcompounds, e.g. butyl acrylate. In addition to these monomers, othersystems were investigated, which to some extent have gained a measure oftechnical importance. Examples of these are: ethylene glycoldimethacrylate and oligoethylene glycol dimethacrylates, (meth)-acrylicester of tricyclo[5.2.1.0²,6 ] decane, glycerine (meth)acrylate,bisphenol-A-derivatives, perfluoborated dimethacrylates, aromaticdiester-dimethacrylates, aromatic diether dimethacrylates and aromaticester ether dimethacrylates, urethane dimethacrylates, diureadimethacrylates, and other compounds. From the vast relevant literature,the following are mentioned as examples thereof: Polymer Science andTechnology 14, 357, 373 and 379 (1981); J. Dent. Res. 58, 1544 and 1981(1979), J. Dent. Res. 58, Abstr. No. 1216, 395 (1979), J. Dent. Res. 49,810 (1970) and 52, 731 as well as 1128 (1973), U.S. Pat. Nos. 4,131,729,3,066,112, 3,179,623, 3,810,938 as well as German Application Nos.2,432,013, 2,312,559 and 2,411,760. In order to improve cohesion, toadjust to suitable viscosity for application purposes, and to reduce thevolume contraction during hardening, polymers are mixed with themonomers in the adhesive component. Examples thereof arepolymethylmethacrylates, polychloroprene, chlorosulfonated polyethylene,nitrile rubbers and/or polyurethanes.

The classical hardeners for room temperature polymerizable methacrylatesystems consist of benzoyl peroxide as the initiator and tertiaryaromatic amines, especially N,N-diemthyltoluidine, as the accelerator.

Today there is a broad pallet of accelerators at our disposal. Also ofimportance are, in this connection, new hardener systems based onorganoboron compounds, which when exposed to oxygen in the air willinitiate the polymerization reaction, thereby making them particularlysuitable for work at room temperature. New hardening systems based onsuch organoboron compounds are the subject matter of a number of priorpatent applications of the applicant.

Reaction adhesives of the organoboron type exhibit a number of usefulproperties. For example, they exhibit a broad spectrum of applicationsfor various surfaces with little requirements for pretreatment of thesurfaces, they harden quickly if desired even at room temperature, andthrough the proper selection of reactive monomers or monomer mixturesthey can be adjusted to give good flexibility values for the adhesivelayer. High stress shearing strengths can be obtained. When working withthese adhesives, the so-called open time can be regulated. The adhesivebond will exhibit less shrinkage and good reproducibility, whileexhibiting good resistance to solvents and temperatures.

The dominant constituents of the adhesive components are stillmono(meth)-acrylates, which exhibit high vapor pressure. However, theuse thereof not only causes an offensive odor, but consequently theadhesive component, for example for No-Mix applications, can only bestored open for a short while.

Bismethacrylates normally have higher boiling points. A number of thesetypes, especially bismethacrylates with high molecular weight, arenormally solid and therefore can be used as monomers in adhesives toonly a minor extent. Furthermore, with respect to bismethacrylates withlow molecular weights, the distance between the functional groups issmall and the corresponding polymers are highly cross linked and have atendency to become brittle.

DESCRIPTION OF THE INVENTION

The present invention has as its object the formulation of new reactivemonomers based on acrylates or methacrylates (referred to hereinafterindividually and collectively as (meth)-acrylate compounds) whichexhibit a number of desirable properties in their use and in thebondings which utilize them. These new monomers exhibit low volatility,based on their low vapor pressure. Despite their high molecular weight,they either exist as, or can be formulated into, a liquid or at least aviscous spreadable paste at room temperature. If they are solids at roomtemperature, they nonetheless exhibit good miscibility with theadditional components normally used with adhesive systems. Additionally,use of the new monomers results in very strong elastic bonds.

The technical solution to the problems to which the present invention isdirected is based on the fact that (meth)-acrylate derivatives ofcertain polyester-oligomers are able to optimally combine the desiredtechnical effects.

The object of the present invention accordingly, in one of its firstembodiments, relates to new (meth)-acrylate compounds with terminal(meth)-acrylic acid groups on an oligomer chain, which have lowvolatility and which are liquid to solid at room temperature, andwherein the oligomer chain is present as a polyester-oligomer that isformed from hydroxycarboxylic acids.

The new (meth)-acrylate compounds contain one or preferably two(meth)-acrylate groups on the polyester-oligomer chain. Also, mixturesof these types of compounds with one or with two (meth)-acrylate groupsfall within the scope of the invention. For practical use, the moreimportant types have two (meth)-acrylate groups in the molecule, whereinthese functional groups are preferably situated terminally on theoligomer chain in such a manner that both terminal units (α,ω-positions) of the oligomer chain are each substituted with a(meth)-acrylate group.

The polyester-oligomer chain is formed from monohydroxy-monocarboxylicacids, wherein the oligomer chains contain the structural characteristic##STR1## in which R is a straight or branched chain alkyl group, anunsubstituted or alkyl substituted cycloalkyl group, or an unsubstitutedor alkyl substituted phenyl group, with R preferably having from 1 to 20carbon atoms, more preferably from 2 to 10 carbon atoms, and mostpreferably from 2 to 7 carbon atoms; and n is an integer dependent onthe selection of the R group, and is preferably chosen so that the meanmolecular weight of the polyester-oligomer chain is in the range of fromabout 200 to about 600, more preferably about 300 to about 500.

The above polyester-oligomer chains are obtained through oligomerizationof a hydroxycarboxylic acid, or a mixture of hydroxycarboxylic acids, ofthe formula ##STR2## wherein R has the meaning given above. Especiallyimportant hydroxycarboxylic acids for the formation of thesepolyester-oligomer intermediates of the new (meth)-acrylate compoundsare glycolic acid, the isomers of lactic acid, the isomers of α- orβ-hydroxypropionic acid, the isomers of α-, β- or γ-hydroxybutyric acid,o-hydroxybenzoic acid (salicylic acid), m-hydroxybenzoic acid and/orp-hydroxybenzoic acid. Also, mixtures of two or more hydroxycarboxylicacids can be employed, in which case the R group defined above can havemore than one structure in the polyester-oligomer chain, depending onthe mixture of hydroxycarboxylic acids chosen for its preparation.

The polyester-oligomers are best prepared by the use of monofunctionaland/or preferably by the use of difunctional coreactants, which fulfilla many faceted function. On the one hand, when using these reactants,control of the mean molecular weight of the polyester-oligomers andadjustment of the desired viscosity range is achieved. On the otherhand, through the selection of the functional groups of the coreactantsused it is possible to form on the polyester-oligomers uniform terminalhydroxyl groups or terminal carboxyl groups, which is normally not thecase with polymers or oligomers of a hydroxycarboxylic acid. Finally, byusing selected monofunctional coreactants, it is possible to eliminateone reactive terminal group of the polyester-oligomer, so that for thistype of compound only one reactive function is available for thesubsequent attachment of the (meth)-acrylate group. By suitableadmixture of mono-functional and difunctional coreactants it is possibleto obtain predetermined mixture ratios of mono-(meth)-acrylate compoundsand bis-(meth)-acrylate compounds.

As the monofunctional coreactants, monoalcohols, mono-carboxylic acids,and/or monoamines, i.e. primary, secondary and/or tertiary monoamines,can be employed. Difunctional coreactants for the preparation of thepolyester-oligomers are difunctional alcohols or dicarboxylic acids, orfunctionally reactive dicarboxylic acid derivatives, especially thecorresponding anhydrides, esters, halides and the like.

If oligomers of the described type are prepared through cocondensationof hydroxycarboxylic acids and diols, there are obtainedpolyester-oligomers with terminal hydroxy groups. The quantity of diolsused, together with the reaction conditions, determine the meanmolecular weight of the resulting polyesteroligomers. On the other hand,if the oligomers are obtained through cocondensation ofhydroxycarboxylic acids with dicarboxylic acids or reactive dicarboxylicacid derivatives, there is obtained polyester-oligomers with terminalcarboxyl groups or derivatives of carboxyl groups. The coreactant actsas a control, standardizes the terminal reactive groups, and regulatesthe molecular weight. Information known in the art for the manufactureof polyesters or copolyesters is also applicable to the present process.The use of monoalcohols and/or monoamines will cause the desiredblocking of the terminal carboxylic acid groups in thepolyester-oligomers, while the use of monocarboxylic acids blocks theterminal hydroxyl group positions on the oligomers.

In all instances described herein, modified polyester-oligomers areformed which can be easily converted by known methods to (meth)-acrylatecompounds. For example, if there are terminal hydroxyl groups on thepolyester-oligomers, the (meth)-acrylic acid group is introduced throughesterification or transesterification or by a comparable reaction withacrylic acids or acrylic acid esters and/or especially the correspondingmethacrylic acid compounds. Also, if there are terminal carboxyl groupsin the polyester-oligomers, the desired (meth)-acrylate group canreadily be attached by known methods. Suitable here, for example, is thereaction of the oligomer intermediate product with glycidyl esters ofacrylic acid or methacrylic acid. By splitting of the glycidyl group,the (meth)-acrylate group is attached via the glyceride group to themonocarboxylic or dicarboxylic acid formed as the intermediate.

In general, the selection of the monofunctional or difunctionalcoreactants, which are used herein in only minor amounts, can be madepractically without limitations. These reactants can be based onsaturated or olefinically unsaturated aliphatic or cycloaliphaticgroups, or they can be aromatic in nature, e.g. phenyl or alkylsubstituted phenyl. Generally, they do not contain more than 25 carbonatoms, and preferably not over 15. Suitable diols contain, for example,2 to 20 carbon atoms, preferably 2 to 10, and more preferably 2 to 6carbon atoms. The same limitations also apply for the correspondingdicarboxylic acids. Examples of suitable diols include ethylene glycol,diethylene glycol, triethylene glycol, tetraethylene glycol, propyleneglycol, dipropylene glycol, 1,3-butylene glycol, 1,4-butylene glycol,2,2-dimethyl-1, 3-propanediol, 2,2,4-trimethyl-1, 6-hexanediol,1,4-cyclohexanedimethanol, 1,5-pentanediol, 1,6-hexanediol,1,10-decanediol and 2,2-bis-(4-hydroxycyclohexyl)-propane.

Examples of dicarboxylic acids that can be employed include: oxalicacid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelicacid, suberic acid, azelaic acid, sebacic acid, isosebacic acid,nonanedicarboxylic acid, decanedicarboxylic acid, undecanedicarboxylicacid, dodecanedicarboxylic acid, phthalic acid, hexahydrophthalic acid,isophthalic acid, terephthalic acid and biphenyldicarboxylic acid. Asacid anhydrides, examples include: succinic anhydride, glutaricanhydride, phthalic anhydride, itaconic anhydride, citraconic anhydride,as well as alkenylsuccinic anhydrides.

It is understood that in all cases, i.e. for the hydroxy-carboxylicacids as well as for the coreactants, not only the free reactivecomponents of the type given above can be used, but also such reactivederivatives can be used which form by known methods under conditions ofesterification or transesterification the desired polyester-oligomers ofa predetermined molecular weight. Suitable in this connection are, forexample, the esters of hydroxycarboxylic acids as well as lactones orlactams of hydroxycarboxylic acids, which when reacted with diols ordiol esters can be transesterified. The manufacture of thepolyester-oligomers as well as their conversion to the (meth)-acrylatecompounds is carried out by known methods, for example, by reaction inthe presence or in the absence of solvents and if desired in thepresence of catalysts, especially esterification catalysts.

Within the scope of the invention are not only the difunctional(meth)-acrylate compounds described above, and not only themonofunctional (meth)-acrylate compounds described above, but alsomixtures of difunctional and monofunctional (meth)-acrylate compounds.Should such mixtures of difunctional and monofunctional (meth)-acrylatecompounds be desired, then in the preferred embodiment, the quantity ofthe monofunctional component is not in excess of 95 mole percent basedon the mixture of the monofunctional and difunctional compounds.Preferred are mixtures thereof in which the content of monofunctionalcompounds is not over 50 mole percent, and preferably not over 10 molepercent.

The new (meth)-acrylate compounds are valuable constituents in reactionadhesives of known composition. Therefore, they are advantageously usedin two component reaction adhesive systems of the type initiallydescribed above, i.e. where the other component (activator or hardenercomponent) contains an initiator to initiate free radicalpolymerization. They can be used not only in conventional(meth)-acrylate systems but also in No-Mix adhesive systems. They aresuitable for use in the so-called construction adhesives to bond metal,wood, glass, ceramics, and/or synthetic materials.

In a preferred embodiment of the invention, the new (meth)-acrylatecompounds are flowable or, at least, still paste-like and spreadable atroom temperature, and therefore they can be used as the main componentor even as the sole polymerizable adhesive component in the reactionadhesives. It is thereby preferred that the liquid (meth)-acrylatecompounds of the invention have a viscosity at room temperature in therange of from about 2000 to 70,000 mPas, preferably in the range ofabout 3000 to 50,000 mPas. Solid (meth)-acrylate compounds of thepresent type are readily soluble in liquid polymerizable components,such as methyl meth-acrylate, so that such solid compounds of theinvention in admixture with liquid conventional monomer constituents arethereby converted in a simple manner to a technically desirable liquidadhesive component.

As is discussed above, as the initiator component for the polymerizationand curing of adhesive systems, organoboron compounds can be used aswell as systems based on benzoyl peroxide. The organoboron typeinitiators are all based on reactive boron components: they have thesame reactivity as the known lower boron alkyls; however, they all showa definite decreased tendency for spontaneous ignition. This makes itpossible to handle them easily and without danger. The organoboroncompounds preferred for use herein show only a slow loss in activitywhen used in the presence of air. They can be used as separate hardenercomponents in two component adhesive systems; it is also possible to usethem as primers in systems of the so-called no-mix adhesives. Theboron-containing hardeners preferred for use in the practice of theinvention will guarantee high strength of the adhesive bond or of the insitu formed synthetic components. The rate of hardening can becontrolled and therefore adjusted to the desired conditions of use. Thestructure of the initiator component guarantees good adhesion of theadhesives for bonding materials together. The hardeners of the inventionto be used herein, based on organoboron compounds, are also described inthe laid open European Patent Applications No. 81109074.5 (D 6144 EP)and No. 81109073.7 (D 6246 EP).

Especially important are the organoboron compounds and systems which aredescribed in prior German Patent Applications Nos. D 6391 (P 31 43945.4), D 6460 (P 32 01 780.4), D 6461 (P 32 01 731.6), D 6517 (P 32 07264.3), and D 6548 (P 32 07 263.5).

Suitable initiators for the new systems can therefore be selected fromthe following groups of boron compounds:

(a) Boron alkyls with sterically hindered alkyl groups of the generalformula ##STR3## wherein R' and R are aliphatic monocyclic or dicyclicgroups with 3 to 25 carbon atoms, and R_(o) is hydrogen or a hydrocarbongroup, preferably cyclic, having from 1 to 15 carbon atoms;

(b) boron compounds which are the reaction products of dihydroxyaromatic compounds with BH₃ or its alkylated products, having thegeneral formula ##STR4## wherein R₁, R₂ and R₃ are either hydrogen or analkyl group having 1 to 4 carbon atoms, and R₁ and R₂ can be an aromaticand/or an aliphatic cyclic group;

(c) boron compounds of the general formula ##STR5## wherein R₄ is analkyl group having 1 to 6 carbon atoms.

As boron alkyl compounds, there can be used a number of known boronalkyls which can be manufactured according to known methods. Typicalrepresentatives of such boron compounds are, for example,9-borabicyclo[3.3.1]nonane, diisopinocampheyl borane,dicyclohexylborane, thexylborane(2,3-dimethyl-2-butylborane),3,5-dimethylborinane, and diisoamylborane. From these compounds thefirst named 9-borabicyclo[3.3.1]nonane is preferred for practicalreasons.

A compilation of possible methods for the preparation of these boroncompounds can be found in the monograph by Herbert C. Brown, 1975"Organic Synthesis via Boranes", Publisher John Wiley & Sons. Asinitiators there can be used hydroborated products of dialkylboranes andolefins. As olefins, there can be used butene, isobutene, hexene,cyclohexene, vinyl chloride, allyl chloride, allyl amine, methacrylicacid methyl ester, vinyl acetate, or crotonic acid methyl ester. Amongthe compounds suitable for use herein should be mentioned for example:diisopinocampheylbutyl boron, thexylcyclohexylcyclopentyl boron,thexyllimonyl boron, trinorbornyl boron,B-butyl-9-borabicyclo[3.3.1]nonane,B-isobutyl-9-borabicyclo[3.3.1]nonane,B-[2-(4-cyclohexenyl)-ethyl]-9-borabicyclo[3.3.1]nonane,B-cyclopropyl-9-borabicyclo[3.3.1]nonane,B-p-tolyl-9-borabicyclo[3.3.1]nonane, and B-tert.butyl-3, 5-dimethylborinane. Additional products that are suitable for use herein are thereaction product of 1,2-dihydroxybenzene (pyrocatechol) with boronhydride (catechol borane), and tri-n-butylboroxin.

Additional especially preferred initiators or hardeners are describedunder (d) below:

(d) These starter systems of the invention consist of a homogeneousmixture of at least one organoboron compound which is activated by air,and an organic oligomer or polymer which is liquid to solid at roomtemperature and which is inert to the organoboron compound. Thedesignation "homogeneous mixture" is understood to include single phasemixtures which are single phase at storage temperatures and usetemperatures, which are characteristic of true solutions.

As organoboron compounds, there are suitable, first of all, boron alkyland/or boron aryl compounds or the corresponding organoboron hydridecompounds. Boron alkyl compounds or boron alkyl hydrides are anespecially preferred class of materials. Preferred embodiments includecompounds of the type:

R₁ R₂ R₃ B,

and/or R₁ BH₂,

R₁ R₂ BH,

wherein in these general formulas, the groups R₁, R₂ and R₃ arehydrocarbon groups, especially alkyl groups which can also includeheteroatoms, especially O, N and/or S. If at least two such organicgroups are attached to the boron atom, they can form a ring system oftheir own. The borons substituted with hydrocarbon groups, in theirpreferred embodiment, do not contain more than about 30 carbon atoms,preferably not more than about 25 carbon atoms. It is more preferredthat each organic radical on the boron does not contain more than about15 carbon atoms. As boron-containing initiator components, or for thepreparation of suitable boron-containing initiator components,organoboron monohydride compounds, preferably the dialkylboronmonohydrides, are particularly suitable for use.

A typical example of such boron compounds is, for example,9-borabicyclo[3.3.1]nonane (9-BBN), which is listed under (a) above andis preferred for practical reasons. As boron initiators in thisembodiment, there can also be used simple trialkylboranes such ashydroborated products of mono- or especially dialkyl boranes and olefinssuch as are described above.

As solvents with very low vapor pressures, there can be used oligomersor polymers which are inert toward the organoboron compounds. There areno restrictions with respect to the structure thereof provided thatthere is a homogeneous miscibility between those used as solvents andthe organoboron compounds. Suitable, therefore, are all polymers,polycondensates and/or polyaddition products which fulfill the aboverequirements. The average molecular weight of these oligomers orpolymers as solvents lie in the range of 200 to 50,000,000 grams/mole.Depending on structure and molecular weight, these solvents can have lowviscosity and be flowable to solid at room temperatures. It is desirablethat the mixtures of materials containing organoboron compounds beviscous, flowable, or spreadable at room temperature. However, this isnot a prerequisite for the effectiveness of the starter systems used asinitiators in accordance with this invention. On the contrary, thestorage stability of the mixtures of materials which are solid at roomtemperature are particularly good. Suitable polymer solvents for use inthis connection are, for example, polyethers, polyesters, polyamides,polyurethanes, polysiloxanes and the like. For the manufacture offlowable systems, there can be used oligomers that are liquid at roomtemperature having viscosities in the range of 1000 to 70,000 mPa's(room temperature) and these are especially interesting. The polyestersand the polyamides especially can be used in many ways in the practiceof the invention. They can, as well as the other polymeric solvents, bemanufactured according to known methods and, in this case, for example,through polycondensation of dicarboxylic acids with diols or diaminesand, if desired or required, with the application of monofunctionalreactants to modify or regulate the mean molecular weight. Preferredherein, as a rule, are saturated dicarboxylic acids and saturatedglycols having up to 15 carbon atoms, preferably up to 10 carbon atomsin the molecule. In an analogous fashion, the above also applies toamines or diamines for the manufacture of polyamides. Suitablepolyethers are, for example, polyethylene oxides or polypropylene oxideshaving a molecular weight in the required range. In this connection, agood knowledge of polymer chemistry is desirable. For the preparation ofstarter systems, the organoboron compounds are dissolved in the inertorganic oligomers or polymers with complete exclusion of oxygen. Ifnecessary, slight heat can be applied. It is, for example, possible inorder to accelerate the dissolution to heat the mixture to a temperatureup to 100° C., preferably about 70° C. When using oligomers or polymersthat are solid at room temperature, the use of inert liquid solvents issuggested. Suitable are known solvents for organoboron compounds such astetrahydrofuran or polyethers such as diethylene glycol dimethyl ether,or esters, halogenated hydrocarbons, and the like. When using theseliquid adjuvants, after a homogeneous mixture is obtained the adjuvantsare evacuated off, and the boron alkyl/oligomer mixture isolated. Thismixture should be stored in closed vessels, preferably under an inertgas such as under nitrogen. The content of organoboron compounds in suchstarter systems is usually not over about 70% by weight and, preferably,not over about 50% by weight based on the total weight of the mixture.It is also preferred that the content of organoboron compounds is atleast about 1 wt. % of the total weight of the system, so thatquantities of about 1 to 50 wt. %, especially 3 to 50 wt. % areparticularly suitable. Another important class of compounds forpractical application involves the use of polymeric organoboroncompounds as initiator components which are stabilized against exposureto air. These compounds are described under (e) below:

(e) the characteristics of this class of organoboron hardeners are thatpolymeric organoboron compounds are used which have as substituents on apolymer matrix, borane and/or organoboron groups stabilized againstexposure to air. These boron-containing groups are preferably attachedthrough B--C bonds to the polymer matrix. So long as theboron-containing groups are not the boryl group (--BH₂) itself, theboron-containing substituents in the polymer matrix in a furtherpreferred embodiment have attached to the boron, with at least oneadditional B--C bond, one or two organic radicals. The preferred groupsare hydrocarbon groups which can also contain heteroatoms, especially O,N and/or S. Suitable substituents on the boron are, in particular,alkyl, cycloalkyl and/or aryl groups which can be on one or both of thefree valences of the boron which are not attached to the polymer matrix.When such organic groups other than hydrogen are in both boron valences,then they can together form a ring system. When compared to the usualboron alkyl hardeners, the oligomeric and polymeric boron compoundsexhibit definite advantages. They are not self-igniting and have littlerequirements during storage. The activity of such hardeners remains evenafter long storage in air. The compatibility of the polymerizablecomponents with the hardener can be assured by suitable selection of thepolymer matrix in each instance. As a rule, for the hardening of themonomer components, the quantity of oligomeric or polymeric organoboroncompounds required is very small.

These polymeric boron compounds can be obtained in a simple manner inthat oligomers or polymers which contain addition receptive carbondouble bonds undergo hydroboration, and consequently theboron-containing groups are introduced into at least a portion of theaddition-receptive double bonds. Suitable for hydroboration are diboraneas well as mono- or di-substituted boranes, that is, compounds of thegeneral formula R₄ R₅ BH, wherein in this formula R₄ is an organicgroup, preferably a hydrocarbon group, and R₅ is a hydrogen or anorganic group which can be the same as R₄ or different from R₄, or,together with R₄ and the boron, can form a ring system. The polymermatrix containing ethylenic double bonds, which are available forhydroboration, can be from low viscosity and flowable to solid,depending on their structure and molecular weight. Their mean molecularweight can have values of several million and is usually in the range ofabout 150 to about 3 million. Lower values within this range arenormally preferred, especially those in the range of about 300 to about500,000, and more especially in the range of about 500 to about 10,000.Also here it is desirable that the polymer matrix, and also thepolymeric organoboron compounds obtained from them, be viscous toflowable or spreadable at room temperature. Here, for example, molecularweights of the polymer matrix in the range of about 300 to about 3,000are especially suitable. For the effectiveness of the polymericorganoboron compounds used in the practice of the invention asinitiators, this is not however a prerequisite. On the contrary, thestorage stability of the polymeric organoboron compounds which are solidat room temperature are especially good.

The polymeric matrix prior to hydroboration can be ethylenicallyunsaturated to any degree. Preferred are matrix materials which prior tohydroboration have an iodine number in the range of about 1 to about500, preferably about 5 to about 100, and more preferably about 8 toabout 50.

Ethylenic double bonds available for hydroboration in the startingpolymers can be in the main chain and/or in the side chain substituents.

The polymer matrix can have either a linear or branched structure,although polymeric materials with cross-linked structures are alsopossible for use herein.

As a polymeric matrix, all polymeric types are suitable so long as theycontain double bonds which are available for hydroboration and containno reactive groups which would lead to undesirable secondary reactionswhen the boron-containing groups are introduced into the polymericmaterial.

The polymeric material can also be obtained through polymerization orcopolymerization of olefinically unsaturated components bypolycondensation or by polyaddition reactions. Through suitableselection of polymers from synthesizable monomer types the desiredamount of reactive double bonds for the subsequent hydroboration in thepolymeric material is assured. Especially suitable as the polymer matrixare unsaturated oligomers or polymers which are obtained through apolycondensation reaction. Usable here are all the known polycondensatetypes such as polyesters, polyamides, polyimides, polycarbonates,polyurethanes and the like. Also suitable are oligomers or polymer typeswhich have been obtained through polyaddition reactions. Details of theformation thereof can be found in earlier German Patent Application No.D 6461 (P 32 01 731.6).

The extent of hydroboration in the polymer matrix is limited only by thenumber of double bonds present. It has been found to be advantageous tohave at least a substantial portion of these double bonds convertedthrough the introduction of boron-containing substituents. In apreferred embodiment of this invention at least 30%, and preferably atleast 50% of the orginally present ethylenic double bonds arehydroborated in the polymer matrix.

Especially suitable are such polymeric organoboron compounds wherein atleast 80%, and preferably at least 90% or even at least 95% of theethylenic double bonds have been reacted with the boron-containingcomponent. A practically completely hydroborated material is in mostcases the preferred initiator with respect to the practice of theinvention. For hydroboration there can be used, in addition to diborane(B₂ H₄), organoboron compounds with one or two organic groups, inparticular, hydrocarbon groups. The preferred organic groups are alkyl,cycloalkyl, and/or aryl groups where two of the available groupstogether with the inclusion of the boron atom can form a ring. Thesubstituted hydrocarbon groups preferably do not contain more than 25carbon atoms, more preferably not more than about 15 carbon atoms.

An especially suitable class of organoboron compounds for thepreparation of the polymeric initiator components areorganoboronmonohydride compounds, especially dialkymonohydrides. Atypical representative of such boron compounds is here also9-borabicyclo[3.3.1]nonane, which is preferred for practical reasons.

A further interesting class of organoboron initiators are described asfollows under (f):

(f) In this embodiment the substituted organoboron compounds arecharacterized in that the boronhydride group or organoboron groupcontains a fatty acid ester and/or a fatty alcohol ester. Theseboronalkyl compounds are hydroborated adducts of diborane and/ororganoboron compounds with at least one B--H bond on fatty acid estersand/or fatty alcohol esters wherein at least one portion of the fattyacid group and/or fatty alcohol group contains carbon-carbon doublebonds receptive to addition reactions.

Concerning the composition and preparation of this class of boronalkylcompounds, the following is applicable:

Esters or ester mixtures which serve as the matrix contain on B--C bondsas substituents boronhydride groups and/or organoboron groups. To theextent these boron-containing groups do not represent the boryl group(--BH₂) itself, such boron-containing substituents in a preferredembodiment have attached to the boron with at least one additional B--Cbond one or two organic groups. Preferred groups are hydrocarbon groups,which can optionally contain heteroatoms, especially O, N, and/or S.Suitable substituents on the boron are preferably alkyl, cycloalkyl,and/or aryl groups, which are in one or both valences of the boron whichare not attached to the ester matrix. In the event the organic groupsother than hydrogen are on both boron valences, they can together form aring system.

These boron compounds can be produced in a simple manner, when thestarting material containing the ester matrix having olefinic doublebonds has been subjected to hydroboration with diborane, or preferablywith monosubstituted and especially with di-substituted boranes of thegeneral formula R₆ R₇ BH, wherein in this formula R₆ is an organicgroup, preferably a hydrocarbon group, and R₇ is hydrogen or also anorganic group, which can be the same as R₆ or different from R₆ ortogether with R₆ can form a ring system with the boron. Preferredorganic groups are alkyl, cycloalkyl and/or aryl groups. The hydrocarbongroups which substitute the boron preferably contain not more than 25carbon atoms, preferably not more than 15 carbon atoms. In an especiallypreferred embodiment, R₆ and R₇ together with the boron atom forms aring system which does not exceed the above values for the number ofcarbon atoms. Here also the above mentioned 9-BBN is preferred forpractical reasons. Of decisive importance is the ester base that servesas the matrix. The starting materials for this matrix are characterizedin that they are monofunctional fatty acids and/or monofunctional fattyalcohols which are converted into esters or ester mixtures, wherein atleast one portion of their fatty acid and/or fatty alcohol componentshave a carbon-carbon double bond receptive to addition reactions. Theterms fatty acids and fatty alcohols encompass monofunctional componentsof the named type with a carbon atom number in the range of about 8 to32 carbon atoms, preferably in the range of about 14 to 22 carbon atoms.The unsaturated fatty acids or unsaturated fatty alcohols can be ofsynthetic or natural origin. Preferably there are used singly ormultiply olefinically unsaturated alkene monocarboxylic acids ormonoalkenols of the required carbon number. The carbon chains of thesefatty acids or fatty alcohols can be straight chain and/or branched.

The complementary components forming the esters can be either amonohydroxy or polyhydroxy alcohol or, respectively, a monofunctional ora polyfunctional carboxylic acid. It is possible to have the additionavailable carbon-carbon double bonds in only one constituent, i.e., onlyin the fatty acid or the fatty alcohol; however, both ester formingcomponents can contain olefinic double bonds. For the preparation of theboron alkyl compounds used in the practice of the invention, at leastsubstantial portion of these double bonds will be subjected tohydroboration. In a preferred embodiment, the ester matrix is formedthrough esterification of a monofunctional component (acid or alcohol)with a polyfunctional complementary component (alcohol or acid).

Especially preferred matrix materials are esters of unsaturatedmonocarboxylic acids (unsaturated fatty acids) with polyhydroxyalcohols. As the polyhydroxy ester-forming reaction component,especially suitable are those compounds which have a functionality up to6, preferably with a functionality of 2 to 4. In this preferredembodiment for the matrix for the boron-containing substituents,monocarboxylic acids of the stated carbon number range are esterifiedwith polyhydroxy alcohols, in particular with dihydroxy alcohols,trihydroxy alcohols, or tetrahydroxy alcohols.

It is advantageous to have the polyfunctional ester components with arelatively low number of carbon atoms which, for example, can be in therange of 2 to 10, preferably in the range of 2 to 6 carbon atoms. Aspolyfunctional alcohols, especially suitable are the lower glycols suchas ethylene glycol, propylene glycol-1,2, propylene glycol-1,3, the C₄glycols with terminal and/or internal hydroxyl groups, or thecorresponding C₅ and C₆ compounds. An especially preferred alcohol foruse herein is glycerine or polyhydroxy alcohols of the pentaerythritetype. On the other hand, monofunctional fatty alcohols can be esterifiedwith lower polycarboxylic acids, in particular, with lower dicarboxylicacids or lower tricarboxylic acids.

It is also possible to use synthetic or natural fats and/or oils as theester matrix for the subsequent hydroboration. Unsaturated esters inadmixture with saturated components such as mixtures with saturatedesters and/or in mixtures with different unsaturated esters can be used.

Esters of corresponding fats and/or oils which contain ethylenic doublebonds available for hydroboration can be either low viscosity andflowable to solid depending on their structure and molecular weight.

The unsaturated esters or ester mixtures such as fats, oils and the likecan be ethylenically unsaturated in various degrees prior tohydroboration. Preferred as suitable starting material are those havingan iodine number of up to about 280, preferably in the range of about 1to about 205. Within this range the value of the iodine number of fromabout 5 to about 130 is especially preferred.

The extent of hydroboration of the ester matrix can be selected freelywithin the framework of the total number of available double bonds. Ithas been proved advantageous when at least a substantial portion ofthese double bonds are converted by the introduction of theboron-containing substituents. In a preferred embodiment, more than 30%,preferably at least 50%, and more preferably at least 70% of theethylenic double bonds of those originally available in the ester matrixare hydroborated. Especially preferred are those organoboron compoundsin which, in relation to the reaction starting materials, at least 80%,preferably at least 90%, or even at least 95% of the ethylenic doublebonds contain the boron-containing constituents.

For hydroboration, the unsaturated esters are reacted with the selectedboronhydride compounds under complete exclusion of oxygen. It isadvantageous here to work in the presence of solvents. Suitable are theknown solvents for organoboron compounds, especially tetrahydrofuran,glycol, polyethers such as diethyleneglycol-dimethylether, esters,hydrogen halides, and the like. The reaction is preferably carried outin a temperature range of about 0° to about 100° C., preferably in therange of about room temperature to about 70° C.

In the following examples, which are given for illustration purposesonly, there are described the preparation of various types ofpolyester-oligomers (Examples 1 to 10), then the preparation of the(meth)-acrylate derivatives of these polyester-oligomers (Examples 11 to20) and, finally, the testing of these reactive monomers as constructionadhesives (Example 21).

EXAMPLES 1-6 Oligohydroxycarboxylic acids with hydroxyl end groups

(a) Preparation from glycolic acid and ethylene glycol

In a three-necked flask equipped with stirrer and reflux condenser,glycolic acid and ethylene glycol are introduced under nitrogen. Themixture is heated quickly to 150° C. and then in the course of 6 hoursfrom 150° to 200° C. During this time, the largest portion of the waterof reaction separates, indicating the conversion of the estercondensation. The composition is allowed to cool to about 150° C.,evacuated carefully to 10 Torr and the conversion is completed at 200°C. and 10 Torr. After 30 minutes, the product is removed hot at about150° C. The composition of the starting materials and the properties ofthe oligomers obtained are given in Table 1 (Examples 1-3).

                                      TABLE 1                                     __________________________________________________________________________    Oligohydroxycarboxylic acids with terminal hydroxyl groups from glycolic      acid and ethylene glycol                                                      Adducts             Reaction    Calculated                                         Glycolic acid,                                                                       Ethylene glycol                                                                       water, Acid Molecular Weight                              Example                                                                            moles  moles   % of theory                                                                          number                                                                             g/mole   Appearance                           __________________________________________________________________________    1    3      1        100   14   252      Clear, viscous,                                                               light yellow                         2    4      1       >90    20   294      Viscous, white                       3    6      1       >98    24   410      Wax-like, white                      __________________________________________________________________________

(b) Preparation from lactic acid ethyl ester and ethylene glycol

In a three-necked flask equipped with stirrer and reflux condenser,lactic acid ethyl ester and ethylene glycol are combined. As catalyst,there is added 70 ml of 0.2% methanolic sodium methylate solution andthe mixture is then heated to 150° C. The temperature is then carefullyraised to 180° C., and at this temperature ethanol constantly distillsoff. After completion of the ethanol separation after about 16 hours,the flask is evacuated at a bath temperature of 150° C. at 10 Torr andthe material remaining in the flask is then removed under nitrogen. Thecomposition of the starting materials and the properties of theoligomers obtained are set forth in Table 2 (Examples 4-6).

                                      TABLE 2                                     __________________________________________________________________________    Oligohydroxycarboxylic acids with terminal hydroxyl groups from               lactic acid ethyl ester and ethylene glycol                                                            Products                                             Adducts                  Yield                                                     Lactic acid ethyl ester,                                                                 Ethylene glycol,                                                                       Ethanol,                                             Example                                                                            moles      moles    %    Molec. Wt.                                                                           Appearance                               __________________________________________________________________________    4    2          1        95   193 (Osmosis)                                                                        Clear, viscous,                                                               orange colored                           5    4          1        92   --     Clear, viscous,                                                               brown                                    6    6          1        96   --     Clear, viscous,                                                               reddish brown                            __________________________________________________________________________

EXAMPLES 7-10 Oligohydroxycarboxylic acids with terminal carboxyl groups

General Method

(a) Through conversion of oligohydroxycarboxylic acids having terminalhydroxyl groups with succinic anhydride

EXAMPLE 7

206.3 grams of the oligomer of Example 4, 200 grams of succinicanhydride, and 1 gram of benzyltrimethylammonium methoxide (40% inmethanol) are combined in a three-necked flask equipped with stirrer,reflux condensor, and nitrogen supply, and stirred for 8 hours at 80° C.under nitrogen. The product is characterized by the followingcoefficients:

Acid number: 296

OH number: <3

(b) Preparation from glycolic acid and adipic acid

In a three-necked flask equipped with stirrer and reflux condenser, theadipic acid and the glycolic acid are introduced. The mixture is heatedrapidly under nitrogen to 150° C. and then during the course of 6 hoursthe temperature is raised from 150° C. to 200° C. During this procedure,the main portion of the water of reaction separates, which indicates thedegree of completion of the ester condensation reaction. The mixture iscooled to about 150° C., carefully evacuated under 10 Torr and thereaction is completed at 200° C. and 10 Torr. The product is thenremoved while hot under nitrogen. The composition of the startingmaterials and the properties of the oligomers obtained are set forth inTable 3 (Examples 8-10).

                                      TABLE 3                                     __________________________________________________________________________    Oligohydroxycarboxylic acids with terminal carboxyl groups from glycolic      acid and adipic acid                                                                             Products                                                   Adducts            Yield of      Molec. weight                                     Glycolic acid,                                                                       Adipic acid,                                                                         water of reaction,                                                                     Acid from acid number,                            Example                                                                            moles  moles  %        number                                                                             g mole.sup.-1                                                                          Appearance                          __________________________________________________________________________    8    1      1      >99      620  181      Wax-like, hard                      9    3      1      >98      376  298      Wax-like, soft                      10   4      1      >96      334  336      Wax-like, soft                      __________________________________________________________________________

EXAMPLES 11-20 Oligohydroxycarboxylic acids with polymerizable endgroups

(a) Oligohydroxycarboxylic acids with polymerizable end groups fromoligohydroxycarboxylic acids with terminal hydroxyl groups.

In a three-necked flask equipped with stirrer and water separator, theoligohydroxycarboxylic acids with terminal hydroxyl groups and 1.1equivalents of methacrylic acid per hydroxyl group are introduced. Atthe same time--in relation to the methacrylic acid--equivalentquantities by weight of toluene and also 2% by weight each ofp-toluenesulfonic acid and hydroquinone are added.

The mixture is heated with rapid stirring to the boiling point and thewater of reaction formed is removed with a water separator.

If after 5 hours reaction time less than 90 to 95 weight % of thetheoretical quantity of the theoretically expected water of reaction hasseparated, there is added once again 20% of the originally addedquantity of methacrylic acid with 2 weight % each of paratoluenesulfonicacid and hydroquinone and the reaction is continued.

The reaction is completed when 90 to 95% of the expected water ofreaction has formed. The reaction product after cooling is added totwice its volume of ethanol and filtered. The clear ethanolic solutionis condensed to 1/4 of its original volume with a rotation evaporator,then poured into the same quantity of water and neutralized with sodiumhydrogen carbonate. The organic phase is separated, the aqueous phaseshaken with toluene, the organic phases combined, washed three timeswith water, and dried over sodium sulfate. The solvent is evacuated atroom temperature first in a rotation evaporator and then at 10⁻⁴ Torr.The composition of the starting materials and the properties of thepolymerizable oligomers formed are set forth in Table 4 (Examples11-16).

                  TABLE 4                                                         ______________________________________                                        Oligohydroxycarboxylic acids with polymerizable terminal groups                                  Yield of Water                                                    Diol adduct of Reaction,                                               Example                                                                              from Example                                                                              %           Appearance                                     ______________________________________                                        11     1           >97         Homogeneous,                                                                  low viscosity liquid,                                                         brown                                          12     2           >95         Homogeneous,                                                                  low viscosity liquid,                                                         brown                                          13     3           >95         Homogeneous,                                                                  low viscosity liquid,                                                         brown                                          14     4           >95         Homogeneous,                                                                  low viscosity liquid,                                                         brown                                          15     5           >95         Homogeneous,                                                                  viscous, brown                                 16     6           >90         Homogeneous,                                                                  viscous, brown                                 ______________________________________                                    

(b) Oligohydroxycarboxylic acids with polymerizable end groups fromoligohydroxycarboxylic acids with terminal carboxyl groups

In a three-necked flask equipped with stirrer and reflux condenser areplaced the oligohydroxycarboxylic acid with terminal carboxyl groups and1.0 equivalents of glycidyl methacrylate with 0.1% by weightbenzyltrimethylammonium methoxide and 0.06% by weight of hydroquinone.With stirring, the mixture is heated within 45 minutes to 80° C. and thereaction continued at 80° C. until the acid number has dropped below 35.Normally the reaction goes to completion within 10 to 20 hours.

The composition of the starting material and the properties of thepolymerizable oligomers are set forth in Table 5 (Examples 17-20).

                  TABLE 5                                                         ______________________________________                                        Oligohydroxycarboxylic acids with polymerizable end groups                    Dicarboxylic   Product                                                               acid adduct Acid                                                       Example                                                                              from Example                                                                              number    Appearance                                       ______________________________________                                        17     7           24        Homogeneous, viscous,                                                         yellow                                           18     8           30        Homogeneous, viscous,                                                         light yellow                                     19     9           34        Homogeneous, highly                                                           viscous, light yellow                            20     10          31        Homogeneous, highly                                                           viscous, light yellow                            ______________________________________                                    

EXAMPLE 21 Construction bonding with oligohydroxycarboxylic acids withpolymerizable end groups

With the monomers prepared herein, sandblasted and degreased sheet iron(DIN 53,281/53,283) are used for bonding purposes. Theoligohydroxycarboxylic acids with polymerizable end groups which areprepared herein are used

I. in pure form,

II. in a mixture of 20% by weight hydroxyethylmethacrylate,

III. in a mixture with 20% by weight methylmethacrylate and 5% by weightmethacrylic acid.

(a) To each 5 grams of monomers (I) or the monomer mixtures (II, III)there were added, with intensive mixing, first 0.5% by weightN,N-dimethyl-p-toluidine and then 0.5% by weight of dibenzoylperoxide.The mixtures had pot times between 2 and 8 minutes. The sandblasted anddegreased iron sheets were bonded with the adhesive and after 24 hourstorage at room temperature in air, the stress shearing strengths weredetermined. In a further series of experiments, there was added to each5 grams of monomers (I) or the monomer mixtures (II, III) 1% by weightof dibenzoylperoxide and to an additional 5 grams of monomer, 1% byweight of N,N-dimethyl-p-toluidine. One portion of the iron sheets werebrushed with the peroxide-containing monomer and the other portion withthe di-methyltoluidine-containing monomer.

Differently coated test sheets were paired together and fixed. The testsheets were stored for 24 hours at room temperature and then torn apartin a stress shearing test. The measured stress shearing values arelisted in Table 6. The stress shearing values given are arithmetic meansof 6 bondings each according to (a) and (b) at a stress shearing rate of12 mm/minute.

                  TABLE 6                                                         ______________________________________                                        Stress shearing values for the bonding of iron sheets                         using monomer adhesives based on oligohydroxycarboxylic acids                 with polymerizable terminal groups/Nmm.sup.-2.                                       Comonomers                                                                                          III                                                               II          Methylmethacrylate                               Monomer          Hydroxyethyl-                                                                             20 wt. %                                         from             methacrylate                                                                              methacrylic acid                                 Example  I       20 wt. %    5 wt. %                                          ______________________________________                                        11       15      16          18                                               12       17      20          18                                               13       18      18          19                                               14       13      15          16                                               15       16      16          17                                               16        8      16          16                                               17       11      18          20                                               18       17      21          22                                               19        7      24          23                                               20        6      21          19                                               ______________________________________                                    

What is claimed is:
 1. A (meth)-acrylate compound having two terminal(meth)-acrylyl groups and a polyester oligomer chain that containshydroxycarboxylic acid segments wherein the polyester oligomer chain hasa mean molecular weight in the range of about 200 to about 600 andwherein the oligomer chain contains the structural characteristic##STR6## in which R has from 1 to 20 carbon atoms and is a straight orbranched chain alkyl group, an unsubstituted or alkyl substitutedcycloalkyl group, or an unsubstituted or alkyl substituted phenyl group,and n is an integer chosen to give a molecular weight for the oligomerchain in the above mean molecular weight range.
 2. A (meth)-acrylatecompound in accordance with claim 1 wherein the polyester oligomer chainhas a mean molecular weight in the range of about 300 to about
 500. 3. A(meth)-acrylate compounds in accordance with claim 1 wherein eachhydroxycarboxylic acid segment present in the polyester oligomer chaincontains from 2 to 10 carbon atoms.
 4. A (meth)-acrylate compounds inaccordance with claim 1 wherein each hydroxycarboxylic acid segmentpresent in the polyester oligomer chain contains from 2 to 6 carbonatoms.
 5. A (meth)-acrylate compound in accordance with claim 1 whereineach hydroxycarboxylic acid segment present in the polyester oligomerchain is formed from an acid selected from the group consisting ofglycolic acid, lactic acid, hydroxypropionic acid, hydroxybutyric acid,and hydroxybenzoic acid.
 6. A (meth)-acrylate compound in accordancewith claim 1 wherein said compound also contains at least one moietyderived from a difunctional alcohol, a difunctional carboxylic acid, orthe corresponding anhydrides, esters or halides.
 7. A (meth)-acrylatecompound in accordance with claim 6 wherein any such moiety present insaid compound contains not more than 25 carbon atoms.
 8. A(meth)-acrylate compound in accordance with claim 6 wherein any suchmoiety present in said compound contains not more than 15 carbon atoms.9. A (meth)-acrylate compound in accordance with claim 6 wherein anysuch moiety present in said compound contains from 2 to 10 carbon atoms.10. A (meth)-acrylate compound in accordance with claim 6 wherein anysuch moiety present in said compound contains from 2 to 6 carbon atoms.11. A (meth)-acrylate compound in accordance with claim 6 wherein amixture of a monofunctional compound and a difunctional compound isemployed in the formation of the (meth)-acrylate compound, and whereinthe monofunctional compound is used in quantities not over 50 molepercent of said mixture.
 12. A (meth)-acrylate compound in accordancewith claim 1 wherein said compound has a viscosity at room temperatureof from about 2000 to about 70,000 mPas.
 13. A (meth)-acrylate compoundin accordance with claim 12 wherein the viscosity at room temperature isfrom about 3,000 to about 50,000 mPas.
 14. A (meth)-acrylate compoundwhich is a (meth)-acrylic acid ester having a (meth)-acrylate group on apolyester oligomer chain that contains hydroxycarboxylic acid segmentswherein the polyester oligomer chain has a mean molecular weight in therange of about 200 to about 600, and which compound also contains amoiety derived from a monocarboxylic acid of functionally reactivederivative thereof.
 15. A (meth)-acrylate compound in accordance withclaim 14 wherein the (meth)-acrylate group is obtained by reaction ofthe terminal carboxy group of the polymer oligomer chain with a glycidylester of (meth)-acrylic acid.
 16. A (meth)-acrylate compound containingtwo terminal (meth)-acrylyl groups and an internal structure containinga polyester oligomer chain that contains hydroxycarboxylic acid segmentsand at least one moiety derived from a member selected from the groupconsisting of a difunctional alcohol, a dicarboxylic acid, and areactive derivative of a dicarboxylic acid, in which such moieties donot contain more than 25 carbon atoms, wherein said compound is preparedby the steps of(i) cocondensing at least one hydroxycarboxylic acid ofthe formula ##STR7## wherein R is a straight or branched chain alkylgroup, an unsubstituted or alkyl substituted cycloalkyl group, or anunsubstituted or alkyl substituted phenyl group, with a coreactant whichis one or more of a member selected from the group consisting of adifunctional alcohol, a dicarboxylic acid, and the anhydrides, esters orhalides of the corresponding dicarboxylic acid, wherein such coreactantdoes not contain more than 25 carbon atoms, to form an intermediateproduct containing either two terminal hydroxy groups, two terminalcarboxyl groups, or one terminal hydroxy group and one terminal carboxylgroup; and (ii) reacting any terminal hydroxy groups on the intermediateproduct with (meth)-acrylic acid or an ester thereof, and reacting anyterminal carboxyl groups on the intermediate product with the glycidylester of (meth)-acrylic acid.
 17. A (meth)-acrylate compound inaccordance with claim 16 wherein the step (i) cocondensation is carriedout with a hydroxycarboxylic acid and a difunctional alcohol.
 18. A(meth)-acrylate compound in accordance with claim 16 wherein the step(i) cocondensation is carried out with a hydroxycarboxylic acid and amember selected from the group consisting of a dicarboxylic acid and areactive derivative thereof.
 19. A (meth)-acrylate compound inaccordance with claim 16 wherein in step (i) the R group in thehydroxycarboxylic acid contains from 1 to 20 carbon atoms.
 20. A(meth)-acrylate compound in accordance with claim 19 wherein the R groupcontains from 2 to 10 carbon atoms.
 21. A (meth)-acrylate compound inaccordance with claim 19 wherein the R group contains from 2 to 7 carbonatoms.
 22. A (meth)-acrylate compound in accordance with claim 16wherein in step (i) a mixture of two or more hydroxycarboxylic acids areemployed therein.
 23. A (meth)-acrylate compound in accordance withclaim 16 wherein the compound has a viscosity at room temperature offrom about 2,000 to 70,000 mPas.
 24. A (meth)-acrylate compound inaccordance with claim 23 wherein the viscosity is from about 3,000 toabout 50,000 mPas.
 25. A (meth)-acrylate compound in accordance withclaim 16 wherein in step (i) the at least one hydroxycarboxylic acid isat least one acid selected from the group consisting of glycolic acid,an isomer of α or β-hydroxypropionic acid, an isomer of α-, β- orγ-hydroxybutyric acid, o-hydroxybenzoic acid, m-hydroxybenzoic acid, andp-hydroxybenzoicc acid.
 26. A (meth)-acrylate compound in accordancewith claim 16 wherein a mixture of a monofunctional compound and adifunctional compound is employed in step (i), and wherein themonofunctional compound is used in quantities not over 50 mol percent ofsaid mixture.
 27. A compound containing hydroxycarboxylic acid segmentsand at least one moiety derived from a member selected from the groupconsisting of a difunctional alcohol, a dicarboxylic acid, and theanhydrides, esters or halides of the corresponding dicarboxylic acid, inwhich such moieties do not contain more than 25 carbon atoms, whereinthe compound is prepared by cocondensing at least one hydroxycarboxylicacid of the formula ##STR8## wherein R is a straight or branched chainalkyl group, an unsubstituted or alkyl substituted cycloalkyl group, oran unsubstituted or alkyl substituted phenyl group, with a coreactantwhich is at least one of a member selected from the group consisting ofa difunctional alcohol, a dicarboxylic acid, and a reactive derivativeof a dicarboxylic acid wherein such coreactant does not contain morethan 25 carbon atoms, to form a compound containing either two terminalhydroxy groups, two terminal carboxyl groups, or one terminal hydroxygroup and one terminal carboxyl group.
 28. A compound in accordance withclaim 27 wherein the cocondensation is carried out with ahydroxycarboxylic acid and a difunctional alcohol.
 29. A compound inaccordance with claim 27 wherein the cocondensation is carried out witha hydroxycarboxylic acid and a dicarboxylic acid or the correspondinganhydrides, esters or halides.
 30. A compound in accordance with claim27 wherein the R group in the hydroxycarboxylic acid contains from 1 to20 carbon atoms.
 31. A compound in accordance with claim 30 wherein theR group contains from 2 to 10 carbon atoms.
 32. A compound in accordancewith claim 30 wherein the R group contains from 2 to 7 carbon atoms. 33.A compound in accordance with claim 27 wherein in forming the compound amixture of two or more hydroxycarboxylic acids are employed therein. 34.A compound in accordance with claim 27 wherein the at least onehydroxycarboxylic acid is at least one acid selected from the groupconsisting of glycolic acid, an isomer of α- or β-hydroxypropionic acid,an isomer of α-, β- or γ-hydroxybutyric acid, o-hydroxybenzoic acid,m-hydroxybenzoic acid, and p-hydroxybenzoic acid.
 35. A compound inaccordance with claim 27 wherein a mixture of a monofunctional compoundand a difunctional compound is employed in forming the compound, andwherein the monofunctional compound is used in quantities not over 50mol percent of said mixture.